The impact of mental health on outcome after anterior cervical discectomy: cohort study assessing the influence of mental health using predictive modelling

Background Depression and anxiety are common mental disorders among patients with chronic pain. It is hypothesised that patients suffering from these disorders benefit less from cervical spine surgery than mentally healthy patients. Therefore, this study aimed to quantify the effect of mental health status on functional outcome after anterior cervical discectomy in a post hoc analysis on RCT data. Methods One hundred eight patients from the NECK trial, with radiculopathy due to a one-level herniated disc, underwent anterior cervical discectomy and were included into this analysis. Functional outcome was quantified using the Neck Disability Index (NDI), and mental health status was measured using the Hospital Anxiety and Depression Score (HADS) questionnaire. NDI differences were assessed using generalised estimated equations (GEE), crude means, a predictive linear mixed model (LMM) using baseline scores and over time with an explanatory LMM. Results At baseline, 24% and 32% of patients were respectively depressed and anxious and had statistically significant and clinically relevant higher NDI scores during follow-up. However, in those patients in which the HADS returned to normal during follow-up, NDI values decreased comparably to the non-depression or non-anxiety cases. Those patients that demonstrated persisting high HADS values had convincingly worse NDI scores. A predictive LMM showed that combining baseline NDI and HADS scores was highly predictive of NDI during follow-up. The R shiny application enabled the effective, visual communication of results from the predictive LMM. Conclusion This study shows that mental health status and disability are strongly associated and provides insight into the size of the effect, as well as a way to use this relation to improve preoperative patient counselling. These findings give rise to the suggestion that incorporating mental health screening in the preoperative assessment of patients could help to adequately manage patients' expectations for functional recovery.